<div>
  Delegates the authentication to the underlying Unix operating system user database.
  With this setting, users will be logged into Hudson by entering their Unix username
  and password.

  <p>
  This mode will also allow you to use Unix groups for authorization. For example,
  you can say "everyone in the 'developers' group will have the administrator access". 

  <p>
  This is done through a library called <a href="http://en.wikipedia.org/wiki/Pluggable_Authentication_Modules">PAM</a>,
  which defines its own configuration mechanism. 
  It also works correctly with user database extensions like
  <a href="http://en.wikipedia.org/wiki/Network_Information_Service">NIS</a>.
</div>